1. Field
The disclosed embodiments relate to methods, apparatus and computer program products for detecting heart rate.
2. Background
There are various methods for contactless measurement of the heart rate of a person lying on a bed. A fair share of the methods are based on measuring the almost periodically repeating vibrations of the heart by analyzing the output signal of a force sensor that measures the horizontal or vertical vibrations of the body. An example of a force sensor has been presented in the European patent publication EP 1 563 286.
In addition to the force sensor, the heart rate analysis system requires a signal processing unit that extracts the heart rate from the sensor's signal using a signal processing algorithm. These algorithms conventionally use strategies such as cross-correlation with the beat prototype, as suggested in S. H. Woodward et al., “Estimating heart rate and RSA from the mattress-recorded kinetocardiogram,” Psychophysiology, vol. 44, July 2007, pp. 635-638, bandpass filtering, as suggested in international patent application publication WO 2006/003243, or peak detection, as suggested in S. Okada et al., “Proposal for a Method of Non-restrictive Measurement of Resting Heart Rate in a Lying Position,” Journal of PHYSIOLOGICAL ANTHROPOLOGY, vol. 25, 2006, pp. 299-305.
A drawback of the prior art signal processing algorithms is that typically they are able to detect the heart rate reliably only if the monitored person stays still and does not make any movements that would distort the signal. Movements such as speaking or waving a hand may render the algorithms useless.